package com.primaryedu.encrpy;

import java.io.BufferedInputStream;
import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.UnsupportedEncodingException;

public class Base64Encoder extends FilterOutputStream {  
	  
    private static final char[] chars = {  
     'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',  
     'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',  
     'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',  
     'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',  
     'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',  
     'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',  
     '8', '9', '+', '/'  
    };  
      
    private int charCount;  
    private int carryOver;  
      
    /*** 
    * Constructs a new Base64 encoder that writes output to the given 
    * OutputStream. 
    * 
    * @param out the output stream 
    */  
    public Base64Encoder(OutputStream out) {  
     super(out);  
    }  
      
    /*** 
    * Writes the given byte to the output stream in an encoded form. 
    * 
    * @exception IOException if an I/O error occurs 
    */  
    public void write(int b) throws IOException {  
     // Take 24-bits from three octets, translate into four encoded chars  
     // Break lines at 76 chars  
     // If necessary, pad with 0 bits on the right at the end  
     // Use = signs as padding at the end to ensure encodedLength % 4 == 0  
      
     // Remove the sign bit,  
     // thanks to Christian Schweingruber <chrigu@lorraine.ch>  
     if (b < 0) {  
       b += 256;  
     }  
      
     // First byte use first six bits, save last two bits  
     if (charCount % 3 == 0) {  
       int lookup = b >> 2;  
       carryOver = b & 3;        // last two bits  
       out.write(chars[lookup]);  
     }  
     // Second byte use previous two bits and first four new bits,  
     // save last four bits  
     else if (charCount % 3 == 1) {  
       int lookup = ((carryOver << 4) + (b >> 4)) & 63;  
       carryOver = b & 15;       // last four bits  
       out.write(chars[lookup]);  
     }  
     // Third byte use previous four bits and first two new bits,  
     // then use last six new bits  
     else if (charCount % 3 == 2) {  
       int lookup = ((carryOver << 2) + (b >> 6)) & 63;  
       out.write(chars[lookup]);  
       lookup = b & 63;          // last six bits  
       out.write(chars[lookup]);  
       carryOver = 0;  
     }  
        charCount++;  
      
     // Add newline every 76 output chars (that's 57 input chars)  
        if (charCount % 57 == 0) {  
          out.write('\n');  
        }  
    }  
      
    /*** 
    * Writes the given byte array to the output stream in an  
    * encoded form. 
    * 
    * @param buf the data to be written 
    * @param off the start offset of the data 
    * @param len the length of the data 
    * @exception IOException if an I/O error occurs 
    */  
    public void write(byte[] buf, int off, int len) throws IOException {  
     // This could of course be optimized  
     for (int i = 0; i < len; i++) {  
       write(buf[off + i]);  
     }  
    }  
      
    /*** 
    * Closes the stream, this MUST be called to ensure proper padding is 
    * written to the end of the output stream. 
    * 
    * @exception IOException if an I/O error occurs 
    */  
    public void close() throws IOException {  
     // Handle leftover bytes  
     if (charCount % 3 == 1) {  // one leftover  
       int lookup = (carryOver << 4) & 63;  
       out.write(chars[lookup]);  
       out.write('=');  
       out.write('=');  
     }  
     else if (charCount % 3 == 2) {  // two leftovers  
       int lookup = (carryOver << 2) & 63;  
       out.write(chars[lookup]);  
       out.write('=');  
     }  
     super.close();  
    }  
      
    /*** 
    * Returns the encoded form of the given unencoded string.  The encoder 
    * uses the ISO-8859-1 (Latin-1) encoding to convert the string to bytes. 
    * For greater control over the encoding, encode the string to bytes 
    * yourself and use encode(byte[]). 
    * 
    * @param unencoded the string to encode 
    * @return the encoded form of the unencoded string 
    */  
    public static String encode(String unencoded) {  
     byte[] bytes = null;  
     try {  
       bytes = unencoded.getBytes("UTF-8");  
     }  
     catch (UnsupportedEncodingException ignored) { }  
     return encode(bytes);  
    }  
      
    /*** 
    * Returns the encoded form of the given unencoded string. 
    * 
    * @param bytes the bytes to encode 
    * @return the encoded form of the unencoded string 
    */  
    public static String encode(byte[] bytes) {  
     ByteArrayOutputStream out =   
       new ByteArrayOutputStream((int) (bytes.length * 1.37));  
     Base64Encoder encodedOut = new Base64Encoder(out);  
       
     try {  
       encodedOut.write(bytes);  
       encodedOut.close();  
      
       return out.toString("UTF-8");  
     }  
     catch (IOException ignored) { return null; }  
    }  
      
    public static void main(String[] args) throws Exception {  
     if (args.length != 1) {  
       System.err.println(  
         "Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");  
       return;  
     }  
      
     Base64Encoder encoder = null;  
     BufferedInputStream in = null;  
     try {  
       encoder = new Base64Encoder(System.out);  
       in = new BufferedInputStream(new FileInputStream(args[0]));  
      
       byte[] buf = new byte[4 * 1024];  // 4K buffer  
       int bytesRead;  
       while ((bytesRead = in.read(buf)) != -1) {  
         encoder.write(buf, 0, bytesRead);  
       }  
     }  
     finally {  
       if (in != null) in.close();  
       if (encoder != null) encoder.close();  
     }  
    }  

}
